WASHINGTON  The surviving leaders of the Cali drug cartel, which federal law enforcement agencies say once supplied up to 80% of the cocaine in the USA, pleaded guilty Tuesday to trafficking charges as the government took steps to seize an estimated $2.1 billion in cartel assets.

As part of the plea agreement, U.S. Attorney General Alberto Gonzales said, brothers Miguel and Gilberto Rodriguez Orejuela were sentenced to 30 years in prison, effectively ending a 20-year period in which they were key players in Colombia's violent drug trade.

While Miguel, 62, and Gilberto, 67, were sentenced in Miami, 28 other family members reached a separate pact with the government to surrender their worldwide assets, which court papers say include luxury homes, boats, investment accounts and businesses obtained with drug money.

Although the assets represent the largest drug-related forfeiture in U.S. history, there are no firm estimates of how much the brothers accumulated during their reign of the cartel. None of the relatives was named in the criminal charges.

"It doesn't get any bigger than today," said Drug Enforcement Administrator Karen Tandy. She said the guilty pleas represented the "last nail in the coffin of the Cali cartel."

Tandy said the brothers "defined the word 'kingpins' " with their ruthless oversight of a drug empire. Carolina Barco, Colombia's ambassador to the United States, said the cartel wars claimed hundreds of lives — including those of prosecutors, police and judges — in the South American nation.

Barco, reading a statement from Colombia's attorney general, described the cartel's reign as "one of the most painful chapters in our history."

Since the demise of the Cali group in recent years, there have been signs that the cocaine supply on U.S. streets has declined, said John Walters, director of the White House's Office of National Drug Control Policy. However, he said, smaller groups have taken over many drug-running operations.

Gonzales said the brothers imported more than 200 tons of cocaine into the USA over 20 years. He said the family's assets would go to the countries where they are seized, primarily Colombia.